1. Field of the Invention
This invention relates to the simultaneous (coupled) spin-drawing of continuous filament synthetic fibers from polyester polymer. More particularly, it relates to an improved process for the production of low shrinkage, continuous polyester fibers which are particularly useful in the preparation of tires and industrial products, including industrial belts, conveyor belts, and reinforced elastomeric structures. Still more particularly, it relates to a continuous process for the production of low shrinkage continuous polyester fibers by melt-spinning the polymer followed immediately by drawing the spun fibers wherein the spun fibers are heated substantially immediately above their second order transition temperature by being passed through a steam impinging draw point localizing jet at a steam temperature of 482.degree. C. to 580.degree. C. Yarn thermal shrinkage is reduced and yarn dimensional stability improved with no adverse yarn property changes such as lower strength or higher elongation at break.
2. Description of the Prior Art
There are several prior art processes for reducing thermal shrinkage of polyester yarns; however, this reduction in polyester yarn thermal shrinkage normally can be achieved only by sacrificing strength or mechanical quality, increasing ultimate elongation or elongation at break, or by the expensive alternative of a separate operation following drawing, such as annealing or some other form of heat treatment. It is therefore desirable to have a continuous process which reduces yarn shrinkage without any of the aforementioned disadvantages. In this regard, several processes are known which involve conditions of continuously spinning and drawing filaments.